Nickel-containing reforming catalyst and process

ABSTRACT

An iridium-containing catalyst, particularly one comprising platinum, iridium, and nickel composited with a porous inorganic oxide base, is found useful in hydrocarbon conversion reactions, particularly reforming (hydroforming). Nickel is used in concentrations ranging from about 0.001 to about 0.005 percent based on the total weight of the catalyst. A naphtha or straight run gasoline can be contacted with such catalyst at reforming conditions in the presence of hydrogen to improve the octane quality of the naphtha or gasoline.

Catalytic reforming (i.e., hydroforming) is an established process inthe petroleum refining industry and has been used for improving theoctane quality of naphthas and straight run gasolines for many years.Catalysts used in catalytic reforming are recognized as dual-functional,perhaps more accurately polyfunctional, the catalyst composite includinga component comprising a metal, or metals, or a compound or compoundsthereof, providing a hydrogenation-dehydrogenation (hydrogen transfer)function, isomerization function, hydrocracking function, and/orhydrogenolysis function, and an acidic component providingisomerization, cracking, and/or hydrocracking functions.

The platinum group, or Group VIII noble metals (ruthenium, osmium,rhodium, iridium, palladium and platinum), despite their expense, havebeen long recognized as particularly efficient hydrogen transfercomponents. Platinum per se has, in fact, proven par excellence as ahydrogen transfer component and, in fact, possesses a combination ofproperties which makes it particularly suitable as a component forcommercial reforming catalysts. Conventional reforming catalysts havethus long employed platinum composited with an inorganic oxide base,particularly alumina, to which halogen is added to supply theisomerization function. Platinum catalysts have achieved world-wide usein commercial reforming operations.

Iridium-containing catalysts, i.e., catalysts comprising iridiumcomposited with a porous inorganic oxide, have been widely disclosed inthe literature as useful for a variety of hydrocarbon conversionreactions, viz., reforming, hydrogenation and dehydrogenation,isomerization, hydrocracking, alkylation and dealkylation, steamreforming, and the like. Iridium has also been used in combination withother noble and non-noble metals and composited with inorganic oxidesfor use as hydrocarbon conversion catalysts. Such composites have thusincluded iridium in combination with such other metals as, e.g.,platinum; tungsten; platinum and rhenium; platinum and tin; platinum,rhenium and tin; platinum and lead; platinum and zinc; platinum andthallium; platinum and indium; platinum and lanthanides; and platinumand ruthenium. Some of these catalysts have been specifically describedas useful in catalytic reforming, or hydroforming.

There is a desideratum in the art, occasioned in large part by thewithdrawl of alkyl lead compounds based on ecological considerations,and intensive efforts are again underway to improve the octane qualityof naphthas and gasolines, without use of such additives, or byelimination of such additives, by improving reforming catalysts.Improvements have been made, and new species of catalysts have beendeveloped. Despite this, platinum yet maintains a rank of distinction asa component of commercially viable reforming catalysts. Recently, e.g.,the industry has turned to catalysts which employ bimetallic componentsto provide effective hydrogen transfer for improving the octane qualityof naphthas and gasolines in commercial operations; and even morerecently, attention has turned to multimetallic catalysts, or catalystswhich contain three or more hydrogen transfer components, for use in themanufacture of commercially viable reforming catalysts. While iridiumper se has not proven outstanding as a hydrogen transfer component foruse in commercial reforming, the combination of platinum and iridium hasproven particularly effective, surpassing platinum per se as aneffective hydrogen transfer component for commercial reformingoperations.

Surprisingly, catalysts comprised of composites of platinum and iridiumwith an inorganic oxide base, particularly alumina, suitable inhydrocarbon conversion reactions, particularly reforming were reportedmany years ago, and described in U.S. Pat. No. 2,848,377. Such catalyst,however, did not achieve commercial significance, perhaps due to anumber of drawbacks. For one thing, the catalyst is verysulfur-sensitive and readily deactivated by high sulfur feeds. Moreover,the initial activity of these catalysts is very high, and serious lossof activity occurs quite rapidly due to an acute tendency of theiridium, when exposed to oxygen at elevated temperatures, toagglomerate, and even to form iridium oxide in admixture with theagglomerated metal. The activity of such catalysts is substantiallylowered as a result of the decreased surface area of the metals.Recently, however, it has become practical to regenerateiridium-containing catalysts by redispersal of the metal and, for thisreason, inter alia, platinum-iridium catalysts have achieved a positionof eminence in the present art of catalytic reforming.

Platinum-iridium catalysts possess outstanding activity for use inreforming operations, activity being defined as that property whichimparts the ability to produce aromatics, aromatic production (or octaneimprovement) generally being measured as a function of temperature, feedrate, etc. Platinum-iridium catalysts also possess good selectivitywhich is defined as that property which imparts the ability of thecatalyst to produce high yields of high octane number C₅ ⁺ liquidproducts with concurrent low production of normally gaseoushydrocarbons, i.e., C₁ -C₄ hydrocarbons, or solid carbonaceousby-products, and coke, which form on the catalysts during reforming.These catalysts also possess good stability or activity maintenance,i.e., activity plotted as a function of time, good stability or activitymaintenance being defined as high retention of good activity andselectivity, or continued high activity and stability for prolongedperiods during hydrocarbon conversion, or reforming operations.

While any commercially viable reforming catalyst must possess theseproperties to a significant degree, no catalyst used in real worldoperations can possess all of these properties to the ultimate degree.One of these characteristics may be possessed by a catalyst in admirabledegree, but the poor quality of another of these characteristics mayadversely affect the worth of the catalyst. Thus, a catalyst whichpossesses good selectivity does not necessarily have good activity, andvice versa. A small decrease in C₅ ⁺ liquid yield can thus represent alarge debit in commercial reforming operations. Conversely, the worth ofa catalyst which possesses high selectivity may be jeopardized by theconsiderable capital cost which necessitates large charges of noblemetals containing catalysts. Proper balance between these severalproperties is essential in the commercial world and an improvementgained in one property, or characteristic, cannot be too much offset byloss in another if the catalyst is to prove commercially viable.

Platinum-iridium catalysts have been shown to possess outstandingactivity, and good selectivity. Iridium, however, is not a plentifulmetal and quite expensive. For this reason, inter alia, it is desirableto decrease the amount of iridium employed on the catalyst withoutsignificant decrease of the high activity and selectivity of suchcatalysts. Moreover, it is desired to further improve the basicplatinum-iridium catalyst to the extent possible.

Accordingly, it has now been discovered that a catalyst comprisingcatalytically active amounts of platinum, iridium, and nickel compositedwith a porous inorganic base, notably alumina, is more sulfur-tolerant,considerably more active, and has greater selectivity for producinggasolines at reforming conditions than, e.g., a catalyst otherwisesimilar except that it does not contain nickel. In fact, such catalysthas better selectivity than a catalyst otherwise similar except that itdoes not contain nickel and has an even higher concentration of iridium.Moreover, the activity of such catalyst closely approximates, orapproaches, that of higher iridium-containing catalysts, and at certainconditions has as good as, or better, activity than higheriridium-containing catalysts. A preferred catalyst composition of suchcharacter comprises from about 0.05 to about 3 percent platinum,preferably from about 0.1 to about 1 percent platinum, from about 0.05to about 3 percent iridium, preferably from about 0.1 to about 1 percentiridium, and from about 0.0001 to about 1.0 percent, preferably fromabout 0.0005 to about 0.1 percent of nickel, and more preferably fromabout 0.001 to about 0.005 percent of nickel, based on the total weight(dry basis) of the composition. Preferably, also, the sum total of theplatinum and iridium contained in such catalyst compositions ranges fromabout 0.3 to about 1 percent, and more preferably from about 0.45 toabout 0.70, based on the weight (dry basis) of the total catalystcompositions. In the more preferred compositions, the atom ratio ofiridium:nickel ranges from about 1:1 to about 60:1, and preferably fromabout 10:1 to about 30:1, whereas the atom ratio of the platinum:iridiumranges from about 0.25:1 to about 5:1, and preferably from about 1:1 toabout 2:1. The absolute concentration of the metals used, particularlythe iridium and nickel, has a relationship to the atom ratios employed,as does the nature of the feed and the amount of sulfur and nitrogencontained in the feed. In general, the higher iridium content catalysts(i.e., those containing >0.225 wt.% Ir), for best results, requiregreater concentrations of nickel, and conversely the lower iridiumcontent catalysts (i.e., those containing <0.225 wt.% Ir, for bestresults, require lesser concentrations of nickel. Highly naphthenicfeeds permit the use of higher nickel concentrations with low iridium toachieve the same degree of effectiveness. For paraffinic feeds, lowiridium concentrations require lower nickel concentrations. Conversely,high iridium concentrations require higher nickel concentrations inprocessing paraffinic feeds. As the amount of iridium is decreased, thecatalyst becomes less tolerant to sulfur contained in the feed, althoughthe sulfur tolerance of the nickel-containing catalysts is greater thanthat for the same catalysts without nickel, at all nickel concentrationswithin the ranges specified.

The catalyst compositions also contain from about 0.1 to about 2.5percent halogen, preferably from about 0.5 to about 1.5 percent halogen,and from about 0.001 to about 2 percent, and preferably from about 0.001to about 0.1 percent sulfur, based on the total weight (dry basis) ofthe catalyst compositions. Such catalysts, at optimum conditions,possess superior C₅ ⁺ liquid selectivity, even as compared withcatalysts otherwise similar which contain equal or greater amounts ofiridium, but no nickel. Moreover, the activity of such catalysts, atoptmum conditions, surpasses the activity of catalysts otherwise similarexcept that they contain no nickel, and is not significantly less thancatalysts otherwise similar except that they contain greater amounts ofiridium, but no nickel. In the preferred combinations at optimumconditions, the activity of the catalyst is compared favorably withconventional platinum-iridium reforming catalysts run at optimumconditions, and when slightly decreased, as with certain feeds at lessthan optimum conditions, this disadvantage is more than offset by theenhanced selectivity, the use of a more available and less expensivemetal, one which is less susceptible to agglomeration, and otherdesirable factors. These platinum-iridium-nickel catalysts are far moretolerant to sulfur than catalysts otherwise similar except that theycontain no nickel, particularly at low iridium levels.

The catalysts of this invention are particularly suitable for use aloneor in admixture with other catalysts, and can be used in one or more ofthe several stages (or reaction zones) of a multiple stage reformingprocess, i.e., one wherein a series of reactors is provided with beds ofcatalysts, the beds of which are serially contacted with preheated feed.They are particularly effective for the treatment of paraffinic feeds,and quite suitable in reactors following the first reactor of theseries. In a preferred process of this type, fixed beds of the catalystare contained in individual reactors (or reaction zones), the naphthafeed is reheated in interstage reheater furnaces to reformingtemperatures and, with hydrogen, is passed sequentially through theseveral reactors of the series. The vapor effluent from the last reactorof the series, a gas rich in hydrogen which usually contains smallamounts of gaseous hydrocarbons, is separated from the C₅ ⁺ liquidproduct and recycled to the process to inhibit coke formation on thecatalyst. Hydrogen is produced in net amount in the reaction, which is aparticular advantage in modern refinery operations.

In the practice of this invention, the metals are composited with mildlyor moderately acidic refractory inorganic oxides which are employed assupports, e.g., silica, silica-alumina, magnesia, thoria, boria,titania, zirconia, various spinels and the like including, inparticular, alumina, and more particularly gamma alumina, which speciesare preferred. High surface area catalysts, or catalysts having surfaceareas ranging upwardly from about 100 M² /g. (B.E.T.) are preferred. Inparticular, catalysts having surface areas ranging from about 150 toabout 600 M² /g. prove quite satisfactory.

The platinum and iridium components can be composited or intimatelyassociated with the porous inorganic oxide support or carrier by varioustechniques known to the art such as ion-exchange, coprecipitation withthe alumina in the sol or gel form, etc. For example, the catalystcomposite can be formed by adding together suitable reagents such assalts of platinum and iridium and ammonium hydroxide or ammoniumcarbonate, and a salt of alumina such as aluminum chloride or aluminumsulfate to form aluminum hydroxide. The aluminum hydroxide containingthe salts of platinum and iridium can then be heated, dried, formed intopellets or extruded, and then calcined in nitrogen or non-agglomeratingatmosphere. The nickel is then added to the catalyst by impregnation,typically via an "incipient wetness" technique which requires a minimumof solution so that the total solution is absorbed, initially or aftersome evaporation. The material is then calcined in non-agglomeratingatmosphere and then hydrogen treated, or hydrogen sulfide treated, orboth, in situ or ex situ, to reduce the salts and complete the formationof the catalyst composite.

It is generally preferred, however, to deposit all of the metal on thepreviously pilled, pelleted, beaded, extruded, or sieved particulatesupport material by the impregnation method. Pursuant to theimpregnation method, porous refractory inorganic oxides in dry orsolvated state are contacted, either alone or admixed, or otherwiseincorporated with a metal or metals-containing solution, or solutions,and thereby impregnated by either the "incipient wetness" technique, ora technique embodying absorption from a dilute or concentrated solution,or solutions, with subsequent evaporation to effect total uptake ofliquid. The catalyst is then dried and, if smaller particles aredesired, then crushed to form particles of the desired size ranging,e.g., from about 5 to about 200 mesh (Tyler series), and preferablyparticles of about 1/10 to about 1/50 inch average diameter can be used.The support material can be treated by contact with a single solutioncontaining the desired amounts of platinum, iridium, and nickel, whichis preferred, or treated sequentially by contact with a solution cononeor more metals, and then a solution which contains another metal, ormetals, in the desired amounts. The catalyst from any preparativesequence can then be dried, calcined in a non-agglomerating atmosphereand contacted with hydrogen, or hydrogen sulfide, or both, in situ or exsitu, to reduce part or all of the metal salts and activate thecatalyst.

The incorporation of an acidic or isomerization component within thecatalyst composite is essential. It is preferred to incorporate theacidic or isomerization function required of the catalyst by addition ofhalide, e.g., fluoride, chloride, and the like, particularly chloride,to the catalyst composite to control the rate of isomerization andcracking. This is conveniently and preferably done during the time ofincorporation of the several metals onto the support, or less preferablysubsequent to metals addition to the support. The metals thus can beadded as halide salts of platinum, iridium and nickel during preparationof these catalysts. Generally, from about 0.1 to about 2.5 weightpercent, and preferably from about 0.5 to about 1.5 percent, based onthe weight of the total catalyst composite, of the halide is addedduring manufacture of the catalyst, though halogen can also be added, orreplenished, during regeneration or in situ during normal reformingoperations. A platinum-iridium-nickel catalyst containing from about 0.5to about 1.2 percent halogen, particularly chlorine, has been found toprovide superior selectivity, while yet substantially retaining theactivity of the platinum-iridium catalyst. Moreover, the activity can beretained even when the iridium concentration of the catalyst containingthe triumvirate of metals is reduced to substantially one-half thatwhich is present in the usual bimetallic composition.

The partially dried catalyst, after incorporation of the metals, andhalogen, is then completely dried or calcined in nitrogen or othernon-agglomerating medium, either in situ or ex situ, as related to thereactor in which the naphtha reforming reaction is to be carried out.The general method is to carry out the drying in flowing nitrogen whileraising the temperature stepwise to avoid too high a concentration ofwater vapor. The temperature is generally increased to 800°-1000°F. andthe gas flow maintained until the catalyst is essentially completelydry. It is very important that the catalyst be essentially dry before itis reduced or contacted with hydrogen in order to avoid metalsagglomeration. The catalyst is then reduced, generally with hydrogen ora hydrogen-containing gas, the platinum and iridium being reducedsubstantially to the metallic state before the catalyst is subjected toreforming conditions. The reduction is generally carried out by passingthe hydrogen through the zone of contact with the catalyst at sufficientvelocity to rapidly sweep out the water vapor that is formed. Thetemperature of reduction is not especially critical, but is generallycarried out in the range of about 500° to about 1000°F. The timerequired for reduction of the noble metals is generally short and notmore than an hour, or at least no more than one to four hours, isgenerally required to complete the reduction.

Following the reduction, the catalyst is sulfided by contact with asulfide, generally hydrogen sulfide or compound which will producehydrogen sulfide in situ. The contact of a hydrogen sulfide-containinggas with the catalyst serves a number of functions, and has a profoundinfluence on the reforming performance of the catalyst. In sulfiding thecatalyst, the catalyst is contacted with a dilute gaseous solution,e.g., about 50 to about 5000 ppm, preferably about 1000 to about 3000ppm, of hydrogen sulfide in hydrogen, or hydrogen plus other nonreactivegases. The contacting of the catalyst with this gas is conducted atabout 500° to about 1000°F., preferably from about 700°F. to about950°F., and is continued until hydrogen sulfide is detected in theeffluent gas. Such treatment incorporates from about 0.001 to about 2weight percent, and preferably from about 0.01 to about 0.1 weightpercent sulfur on the catalyst.

Essentially any hydrocarbon fraction containing paraffins, naphthenes,and the like, admixed one with the other or in admixture with otherhydrocarbons, can be converted by means of the catalysts of thisinvention. A suitable feed, e.g., either virgin or cracked,Fischer-Tropsch or mixtures thereof, is contacted at reformingconditions in the presence of hydrogen (once-through, or recycle) with acatalyst composite including a support which contains catalyticallyactive amounts of the metals. Typical feed stream hydrocarbon moleculesare those containing from about 5 to about 12 carbon atoms, or morepreferably from about 6 to about 12 carbon atoms, or more preferablyfrom about 7 to about 10 carbon atoms. Naphthas, or petroleum fractions,boiling within the range of from about 80°F. to about 450°F., andpreferably from about 125°F. to about 375°F., contain hydrocarbons orcarbon numbers within these ranges. Typical fractions thus usuallycontain from about 20 to about 80 volume percent of paraffins, bothnormal and branched, which fall in the range of about C₅ to C₁₂, andfrom about 20 to about 80 volume percent of naphthenes boiling withinthe range of about C₆ to C₁₂. Typical feeds generally contain from about5 through about 20 volume percent of aromatics which boil within therange of about C₆ to C₁₂, typically as produced in the product from thenaphthenes and paraffins.

It is essential, for best results, that the feed contain a small amountof sulfur. Preferably, the feed shall contain from about 0.05 to about10 parts, per million parts of feed (ppm), and more preferably fromabout 0.2 to about 2.0 ppm of sulfur.

The reforming reaction is suitably conducted at temperatures rangingfrom about 600° to about 1050°F., and preferably at temperatures rangingfrom about 850 to about 1000°F. Pressures range generally from about 50to about 750 psig, and preferably from about 100 to about 500 psig. Thereactions are conducted in the presence of hydrogen to suppress sidereactions normally leading to the formation of unsaturated carbonaceousresidues, or coke, which deposits upon and causes deactivation of thecatalyst. The hydrogen rate, once-through or recycle, is generallywithin the range of from about 1000 to about 10,000 SCF/Bbl, andpreferably within the range of from about 2000 to about 5000 SCF/Bbl.The feed stream, in admixture with hydrogen, is passed over beds of thecatalyst at space velocities ranging from about 0.1 to about 25 W/W/Hr.,and preferably from about 0.5 to about 5.0 W/W/Hr.

The invention will be more fully understood by reference to thefollowing selected nonlimiting examples and comparative data whichillusrate its more salient features. All parts are given in terms ofweight except as otherwise specified.

Several catalysts were prepared for demonstrative purposes from portionsof particulate alumina of the type conventionally used in themanufacture of commerical reforming catalysts. The portions of aluminawere impregnated in sequence with solutions of salts of the metals to becomposited therewith, treated and activated and then employed ascatalysts in a series of representative reforming reactions. Theportions of alumina, except in the instance wherein bimetallicplatinum-iridium catalysts (Catalysts A and B), and pltinum catalyst(Catalyst C), all of which were prepared and employed as controls forcomparative purposes, were impregnated with aqueous acid solutionscontaining a mixture of platinum, iridium, and nickel salts (CatalystsD, E, F, and G). The Platinum-iridium catalysts (Catalysts A and B) weresimilarly prepared except that the nickel salt was not added to thesolution and, as regards the pltinum catalyst (Catalyst C), both theiridium and nickel salts were eliminated from the solution.

These series of catalysts were each evaluated in a continuously operatedreactor for reforming naphtha at essentially the same conditions oftemperature, pressure and hydrogen rate. The space velocity of theseveral reactions was varied, as identified in the tabulated data. Thedata related to catalyst preparation, and naphtha reforming, are givenbelow, the data on catalyst preparations being given in the examples anddemonstrations immediately following:

EXAMPLES CATALYST PREPARATIONS

Catalyst A (Platinum-High Iridium)

A portion of high purity gamma alumina extrudates, previously calcined,was crushed and screened to 14-35 mesh (Tyler), then calcined about 2hours in a flow of air or nitrogen at 1000°F. The calcined alumina(50.00 gms) was impregnated with a solution prepared by mixing 6.00 cc.Pt stock solution (25.0 mg Pt/ml and 27.3 mg Cl/cc) and 7.74 cc. Irstock solution (19.4 mg Ir/ml, 25.5 mg Cl/cc.) and diluted toapproximately 65 ml with deionized water. After allowing the solution tostand for a period of one hour, by which time the remaining solution, ifany, was colorless, the catalyst was dried in the vacuum oven to about400°F. The catalyst was then charged to a resistance heated Vycor tubeand heated at 950°-1000°F. in a flow of nitrogen for 3 hours and wasthen reduced in hydrogen at 900°-910°F. for 2 hours. The catalyst wasthen sulfided by treatment with a flowing hydrogen-H₂ S mixture (0.3% H₂S) which was further diluted with hydrogen and nitrogen. This was doneat 900°-910°F. until H₂ S broke through the bottom of the bed and wasdetected with moist lead acetate paper.

The composition of this Catalyst A is as follows:

Pt, 0.29%, Ir, 0.32%; Cl, 0.65%; S, 0.10%

Catalyst B (Platinum-Low Iridium)

A previously calcined portion of gamma alumina particles was calcined,again as in the preparation of Catalyst A. The portion of alumina (50.00gm) was then impregnated with a solution similar to that used in thepreparation of Catalyst A except that it contained one-half as much ofthe iridium stock solution, and 1.81 milliliters of an aqueous solutionwhich contained 48.6 mg of chloride/ml as HCl. After impregnation, thecatalyst was dried, calcined, reduced and sulfided as in the preparationof Catalyst A.

The catalyst composition is as follows:

Pt, 0.30%; Ir, 0.16%; Cl, 0.67%; S, 0.14%.

Catalyst C (Platinum)

Another portion of previously calcined gamma alumina of 14-35 meshparticle size was calcined as in the preparation of Catalysts A and B.Alumina (50.00 g) was impregnated with a solution containing 6.00 mlchloroplatinic acid solution containing 25.0 mg Pt/ml, and 27.3 mg Cl/mland 2.80 milliliters of an aqueous solution which contained 48.6 mg ofchloride/ml as HCl diluted to about 65 ml with deionized water. Theplatinum-alumina precatalyst was dried, calcined and reduced asdescribed in the procedure for Catalyst A. This catalyst was notsulfided as were the iridium catalysts.

The composition of the catalyst is as follows:

Pt, 0.29%; Cl, 0.60%.

Catalyst D (Platinum-Iridium-Nickel)

Again, a previously calcined portion of gamma alumina particles wasfurther calcined as in the preparation of Catalyst A. The alumina (50.00g) was impregnated with a solution similar to that used for Catalyst Bexcept that it contained an additional 0.50 ml of a solution of nickelnitrate with a concentration of 2.50 mg Ni/ml. After impregnation, thecatalyst was dried, calcined, reduced and sulfided as in the preparationof Catalysts A and B.

The composition of the catalysts is given as follows:

Pt, 0.03%; Ir, 0.16%; Cl, 0.69%; Ni, 0.0023%; S, 0.076%.

Catalyst E (Platinum-Iridium-Nickel)

Particulate gamma alumina of 14-35 mesh particle size was calcined,again as in the preparation of Catalyst A. The alumina (50.00 g) wasimpregnated with a solution similar to that used for Catalyst B exceptthat it contained an additional 1.00 ml of a solution of nickel nitratewith a concentration of 2.50 mg Ni/ml. After impregnation, the catalystwas dried, calcined, reduced and sulfided as in the preparation ofCatalyst A, B, and D.

The composition of the catalyst is as follows:

Pt, 0.32%; Ir, 0.14%; Cl, 0.81%; Ni, 0.0045%; S, 0.12%.

Catalyst F (Platinum-Iridium-Nickel)

A portion of previously calcined gamma alumina of 14-35 mesh particlesize was again calcined as in the preparation of Catalyst A. The alumina(50.00 g) was impregnated with a solution similar to that used forCatalyst B except that it contained an additional 2.00 ml of a solutionof nickel nitrate with a concentration of 2.50 mg Ni/ml. Afterimpregnation, the catalyst was dried, calcined, reduced and sulfided asin the preparation of Catalysts A, B, D, and E.

The composition of the catalyst is as follows:

Pt, 0.31%; Ir, 0.16%; Cl, 0.74%; Ni, 0.01%; S, 0.12%.

Catalyst G (Platinum-Iridium-Nickel)

A portion of previously calcined gamma alumina of 14-35 mesh particlesize was again calcined as in the preparation of Catalyst A. The alumina(50.00 g) was impregnated with a solution similar to that used forCatalyst B except that it contained an additional 5.00 ml of a solutionof nickel nitrate with a concentration of 2.50 mg Ni/ml. Afterimpregnation, the catalyst was dried, calcined, reduced and sulfided asin the preparation of Catalysts A, B, D, E, and F.

The composition of the catalyst is as follows:

Pt, 0.31%; Ir, 0.15%; Cl, 0.73%; Ni, 0.025%; S, 0.112%.

REFORMING RUNS

These several catalysts, after their preparation, were allowed to coolunder nitrogen at low flow rate, handled under nitrogen, and storedunder nitrogen and/or purified and dried hydrocarbon, generally normalheptane. Each was subsequently evaluated in extended reforming tests ina small continuous flow, once-through, or non-cyclic, reactor with atypical highly paraffinic Aramco feed and a typical, more naphthenicBaytown virgin naphtha feed, respectively. The inspections on each ofthe feeds are presented in Table 1 as follows:

                  TABLE 1                                                         ______________________________________                                                           Aramco                                                                              Baytown Virgin                                                          Feed  Naphtha Feed                                         ______________________________________                                        API Gravity          60.2    54.8                                             Octane, RON          40.0    56.3                                             Total Aromatics (Wt.)                                                                              15.1    16.5                                             Total Naphthenes (Wt.)                                                                             22.6    38.5                                             Total Paraffins (Wt.)                                                                              62.7    41.7                                             Distillation (ASTM-D86)                                                       IBP, °F.      212     202                                              5%                   232     220                                              10                   236     222                                              20                   244     234                                              30                   251     240                                              40                   260     245                                              50                   269     258                                              60                   279     267                                              70                   290     280                                              80                   302     293                                              90                   315     312                                              95                   325     327                                              FBP, °F.      381     393                                              ______________________________________                                    

A series of reforming runs, as shown by reference to Tables 2 through 6,were conducted with each of these several catalysts, Catalysts A, B andC being employed as references for determination of the effectiveness ofthe novel catalysts of this invention which employ the triumvirate ofmetals, viz., platinum, iridium and nickel (Catalysts D, E, F and G).Catalysts A and B, the "high iridium" and "low iridium" catalysts,respectively, were employed to reform each of the two feeds,respectively, to each of which was added 1.0 ppm of sulfur, thisconcentration of sulfur being about optimum for the high iridiumcatalyst. The "platinum only" catalyst (Catalyst C) was used to reformthe Aramco feed at generally optimum conditions, the feed containing noadded sulfur. Catalyst D, which contained an optimum concentration ofnickel, as shown by reference to Tables 7 through 12, was employed toreform each of the two feeds, each at different sulfur levels, viz., at1.0 ppm of sulfur and at 0.4 ppm of sulfur, respectively, to obtaincomparisons between the activity and selectivity of Catalysts A, B and Cemployed as standards at the generally optimum conditions of each.Results of tests conducted on Catalysts E, F, and G, containing higherconcentrations of nickel, on only one feed at one sulfur level are givenin Tables 13, 14 and 15 for comparison with Catalyst D, containing anoptimum level of nickel.

Each of the reforming tests was conducted at conditions, inclusive ofthe following:

    Sandbath Temperature, °F.                                                                 925 (Isothermal)                                                              (920°F., E.I.T.).sup.(1)                            Pressure, Psi      200                                                        Hydrogen Recycle Rate, SCF/B                                                                     4800                                                        .sup.(1) Equivalent Isothermal Temperature of catalyst bed.   The space       velocities, which were varied in the several runs, are given in the data     tabulated below, along with the results obtained for the individual runs,     this including for the individual runs the catalyst age, in hours, the     C.sub.5 .sup.+ Product Yield (volume %) and the analyzed Aromatics     Concentration in the C.sub.5 .sup.+ Product (volume %), the latter being     given along with the calculated approximate Research Octane Number (RON).

                  TABLE 2                                                         ______________________________________                                        CATALYST A -- 0.29% Pt; 0.32% Ir; 0.65% Cl                                    Run Conditions:                                                                           Armaco Naphtha at 1.0 ppm S                                                   1.0 W/Hr./W Space Velocity                                                   C.sub.5 .sup.+ Product                                                                    Aromatics in                                           Hours on Feed                                                                            Yield       C.sub.5 .sup.+ Product                                                                    Calculated                                 (End of Balance)                                                                         (Volume %)  (Volume %)  RON                                        ______________________________________                                        18.8       49.8        81.6        106.7                                      25.8       56.5        75.7        1044.3                                     42.8       56.6        75.3        104.2                                      49.8       58.2        73.8        103.6                                      121.8      60.2        70.7        102.3                                      138.8      60.5        71.8        102.8                                      145.8      59.9        72.4        103.0                                      162.8      60.3        72.5        103.0                                      169.8      59.5        72.8        103.2                                      186.8      59.9        71.8        102.7                                      193.8      59.0        73.2        103.3                                      210.8      59.3        72.4        103.0                                      217.8      59.6        71.9        102.8                                      313.8      60.1        70.5        102.2                                      330.8      58.8        71.8        102.8                                      337.8      60.3        71.0        102.4                                      354.8      59.8        71.4        102.6                                      361.8      60.1        71.3        102.5                                      378.8      58.9        71.8        102.8                                      385.8      59.6        70.2        102.1                                      481.8      60.2        71.0        102.4                                      ______________________________________                                    

                  TABLE 3                                                         ______________________________________                                        CATALYST A                                                                    Run Conditions:                                                                           Aramco Naphtha at 1.0 ppm S                                                   2.6 W/Hr./W Space Velocity                                                   C.sub.5 .sup.+ Product                                                                    Aromatics in                                           Hours on Feed                                                                            Yield       C.sub.5 .sup.+Product                                                                     Calculated                                 (End of Balance)                                                                         (Volume %)  (Volume %)  RON                                        ______________________________________                                        22.8       68.7        66.1        100.4                                      29.8       70.4        63.7        99.5                                       46.8       71.2        62.2        98.8                                       53.8       71.6        61.6        98.6                                       125.8      70.2        61.2        98.5                                       173.8      68.9        62.6        99.0                                       189.8      67.8        63.1        99.2                                       196.8      69.7        62.9        99.2                                       268.8      69.8        60.6        98.2                                       285.8      68.5        62.0        98.8                                       292.8      68.1        61.5        98.6                                       309.8      68.4        61.4        98.6                                       316.8      69.7        63.2        99.3                                       333.8      68.5        61.9        98.7                                       340.8      70.0        61.0        98.4                                       357.8      69.0        59.9        98.0                                       364.8      69.2        61.6        98.6                                       436.8      68.4        60.5        98.2                                       453.8      68.6        61.3        98.5                                       460.8      67.6        60.8        98.3                                       477.8      68.8        60.8        98.3                                       484.8      69.6        61.3        98.5                                       501.8      69.2        61.4        98.5                                       508.8      69.1        60.5        98.2                                       535.8      68.1        60.7        98.3                                       542.8      69.6        60.2        98.1                                       ______________________________________                                    

                  TABLE 4                                                         ______________________________________                                        CATALYST A                                                                    Run Conditions:                                                                           Baytown Virgin Naphtha at 1.0 ppm S                                           2.7 W/Hr./W Space Velocity                                                   C.sub.5 .sup.+ Product                                                                    Aromatics in                                           Hours of Feed                                                                            Yield       C.sub.5 .sup.+ Product                                                                    Calculated                                 (End of Balance)                                                                         (Volume %)  (Volume %)  RON                                        ______________________________________                                        19.5       73.5        74.2        103.7                                      26.5       77.3        70.3        102.2                                      43.5       77.5        70.1        102.1                                      50.5       78.8        69.5        101.8                                      122.5      79.6        66.8        100.7                                      139.5      80.1        67.2        100.9                                      146.5      80.0        67.0        100.8                                      163.5      80.0        67.0        100.8                                      170.5      79.7        66.6        100.7                                      187.5      79.6        66.7        100.7                                      194.5      80.7        67.0        100.8                                      211.5      79.9        65.2        100.1                                      218.5      80.8        66.4        100.6                                      290.5      80.1        66.2        100.5                                      307.5      79.7        66.5        100.6                                      314.5      80.3        66.0        100.4                                      331.5      79.4        66.8        100.7                                      338.5      80.8        66.3        100.5                                      355.5      80.5        66.2        100.5                                      362.5      79.0        67.3        100.9                                      379.5      80.1        66.2        100.5                                      386.5      78.1        67.1        100.9                                      458.5      79.9        66.5        100.6                                      475.5      80.7        66.8        100.7                                      482.5      80.3        64.5        99.8                                       ______________________________________                                    

                  TABLE 5                                                         ______________________________________                                        CATALYST B - 0.30% Pt; 0.16% Ir; 0.67% Cl                                     Run Conditions:                                                                           Armaco Naphtha at 1.0 ppm S                                                   1.1 W/Hr./W Space Velocity                                                   C.sub.5 .sup.+ Product                                                                    Aromatics in                                           Hours on Feed                                                                            Yield       C.sub.5 .sup.+Product                                                                     Calculated                                 (End of Balance)                                                                         (Volume %)  (Volume %)  RON                                        ______________________________________                                        26.0       66.9        67.9        100.4                                      50.0       70.1        65.8        99.7                                       122.0      68.4        64.7        99.2                                       146.0      68.3        64.7        99.3                                       170.0      68.9        64.8        99.3                                       194.0      68.6        63.1        98.8                                       218.0      68.6        62.0        98.5                                       290.0      70.1        65.3        99.3                                       314.0      69.6        69.6        98.8                                       ______________________________________                                    

                  TABLE 6                                                         ______________________________________                                        CATALYST C - 0.29% Pt; 0.60% Cl                                               Run Conditions:                                                                           Aramco Naphtha at 0.0 ppm S                                                   1.1 W/Hr./W Space Velocity                                                   C.sub.5 .sup.+Product                                                                     Aromatics in                                           Hours on Feed                                                                            Yield       C.sub.5 .sup.+ Product                                                                    Calculated                                 (End of Balance)                                                                         (Volume %)  (Volume %)  RON                                        ______________________________________                                        23.0       64.6        64.4        99.4                                       46.0       67.1        67.0        99.8                                       69.0       66.0        63.1        99.0                                       92.0       66.3        62.5        98.8                                       116.0      67.7        60.5        98.1                                       139.0      68.1        58.4        97.6                                       162.0      68.8        59.1        97.6                                       185.0      69.6        57.1        97.2                                       ______________________________________                                    

                  TABLE 7 -                                                       CATALYST D - 0.30% Pt; 0.16% Ir; 0.0023% Ni; 0.69 Cl                          Run Conditions:                                                                           Aramco Naphtha at 1.0 ppm S                                                   1.0 W/Hr./W Space Velocity                                                   C.sub.5 .sup.+Product                                                                     Aromatics in                                           Hours on Feed                                                                            Yield       C.sub.5 .sup.+ Product                                                                    Calculated                                 (End of Balance)                                                                         (Volume %)  (Volume %)  RON                                        ______________________________________                                        25.7       61.1        74.0        103.7                                      49.7       61.0        71.9        102.8                                      145.7      62.6        72.2        102.9                                      169.7      62.7        71.5        102.7                                      193.7      63.3        71.8        102.8                                      217.7      61.0        72.0        102.8                                      306.7      63.2        72.9        103.2                                      313.7      62.8        71.4        102.6                                      ______________________________________                                    

                  TABLE 8                                                         ______________________________________                                        CATALYST D                                                                    Run Conditions:                                                                           Aramco Naphtha at 1.0 ppm S                                                   1.0 W/hr./W Space Velocity                                        Note: The catalyst for this run has the same composition                            as other catalysts designated as "Catalyst D"                                 except that it is a 1/16" extrudate. -                                             C.sub.5 .sup.+ Product                                                                    Aromatics in                                           Hours on Feed                                                                            Yield       C.sub.5 .sup.+ Product                                                                    Calculated                                 (End of Balance)                                                                         (Volume %)  (Volume %)  RON                                        ______________________________________                                        23.7       60.9        74.9        104.0                                      47.7       62.1        69.9        102.0                                      119.8      63.5        68.6        101.5                                      143.7      62.7        69.9        102.0                                      167.7      63.7        70.2        102.1                                      191.7      64.5        70.4        102.2                                      215.7      63.7        70.4        102.2                                      287.7      62.3        70.5        102.2                                      359.7      62.0        70.2        102.1                                      ______________________________________                                    

                  TABLE 9                                                         ______________________________________                                        CATALYST D                                                                    Run Conditions:                                                                           Aramco Naphtha at 0.4 ppm S                                                   1.0 W/Hr./W Space Velocity                                                   C.sub.5 .sup.+ Product                                                                    Aromatics in                                           Hours on Feed                                                                            Yield       C.sub.5 .sup.+ Product                                                                    Calculated                                 (End of Balance)                                                                         (Volume %)  (Volume %)  RON                                        ______________________________________                                        22.6       61.8        76.1        104.5                                      46.6       64.0        72.5        103.0                                      118.6      59.9        70.3        102.2                                      142.6      60.9        74.9        104.0                                      190.6      59.1        74.0        103.7                                      214.6      59.7        73.4        103.4                                      286.6      57.0        74.6        103.9                                      311.6      58.4        73.6        103.5                                      ______________________________________                                    

                  TABLE 10                                                        ______________________________________                                        CATALYST D                                                                    Run Conditions:                                                                           Aramco Naphtha at 0.4 ppm S                                                   2.6 W/Hr./W Space Velocity                                                   C.sub.5.sup.+ Product                                                                     Aromatics in                                           Hours on Feed                                                                            Yield       C.sub.5.sup.+ Product                                                                     Calculated                                 (End of Balance)                                                                         (Volume %)  (Volume %)  RON                                        ______________________________________                                        23.4       78.7        71.8        102.7                                      47.7       74.8        62.6        99.0                                       119.4      74.6        60.6        98.2                                       144.4      73.7        61.1        98.4                                       168.4      73.0        61.3        98.5                                       192.4      71.4        62.3        98.9                                       216.4      70.7        61.8        98.7                                       288.4      70.3        61.7        98.7                                       312.4      69.7        61.1        98.4                                       ______________________________________                                    

                  TABLE 11                                                        ______________________________________                                        CATALYST D                                                                    Run Conditions:                                                                           Baytown Virgin Naphtha at 1.0 ppm S                                           2.7 W/Hr./W Space Velocity                                                   C.sub.5.sup.+ Product                                                                     Aromatics in                                           Hours on Feed                                                                            Yield       C.sub.5.sup.+ Product                                                                     Calculated                                 (End of Balance)                                                                         (Volume %)  (Volume %)  RON                                        ______________________________________                                        23.5       77.8        68.5        101.4                                      47.5       78.8        68.0        101.2                                      119.5      80.5        67.4        101.0                                      143.3      81.6        67.3        100.9                                      167.3      81.0        67.7        101.1                                      191.3      80.5        67.7        101.1                                      215.3      80.7        68.3        101.4                                      287.3      80.5        66.7        100.7                                      304.8      79.7        68.1        101.3                                      ______________________________________                                    

                  TABLE 12                                                        ______________________________________                                        CATALYST D                                                                    Run Conditions:                                                                           Baytown Virgin Naphtha at 0.4 ppm S                                           2.7 W/Hr./W Space Velocity                                                   C.sub.5.sup.+ Product                                                                     Aromatics in                                           Hours on Feed                                                                            Yield       C.sub.5.sup.+ Product                                                                     Calculated                                 (End of Balance)                                                                         (Volume %)  (Volume %)  RON                                        ______________________________________                                        24.5       78.9        71.1        102.5                                      48.5       79.5        70.3        102.2                                      120.5      80.1        68.4        101.4                                      144.5      80.1        70.5        102.2                                      168.5      80.6        69.0        101.6                                      192.5      79.8        69.4        101.8                                      216.5      80.0        69.0        101.6                                      288.5      78.1        70.4        102.2                                      312.5      79.2        70.2        102.1                                      ______________________________________                                    

                  TABLE 13                                                        ______________________________________                                        CATALYST E -- 0.32% Pt; 0.14% Ir; 0.0045% Ni: 0.81% Cl                        Run Conditions:                                                                           Aramco Naphtha at 1.0 ppm S                                                   1.0 W/Hr./W Space Velocity                                                   C.sub.5.sup.+ Product                                                                     Aromatics in                                           Hours on Feed                                                                            Yield       C.sub.5.sup.+ Product                                                                     Calculated                                 (End of Balance)                                                                         (Volume %)  (Volume %)  RON                                        ______________________________________                                        27.4       60.5        72.0        102.8                                      51.4       62.3        68.9        101.6                                      123.4      63.3        65.6        100.2                                      147.4      62.0        66.3        100.5                                      171.4      63.0        68.8        101.5                                      195.4      58.4        68.0        101.2                                      219.4      63.6        66.4        100.6                                      291.4      64.3        66.1        100.4                                      315.4      61.4        68.3        101.3                                      ______________________________________                                    

                  TABLE 14                                                        ______________________________________                                        CATALYST F -- 0.31% Pt; 0.16% Ir; 0.01% Ni: 0.74% Cl                          Run Conditions:                                                                           Aramco Naphtha at 1.0 ppm S                                                   1.0 W/Hr./W Space Velocity                                                   C.sub.5.sup.+ Product                                                                     Aromatics in                                           Hours on Feed                                                                            Yield       C.sub.5.sup.+ Product                                                                     Calculated                                 (End of Balance)                                                                         (Volume %)  (Volume %)  RON                                        ______________________________________                                        24.3       62.9        74.2        103.7                                      48.3       66.4        69.8        101.9                                      120.3      66.4        70.0        102.0                                      144.3      65.7        67.7        101.1                                      168.3      65.7        69.0        101.6                                      192.3      65.6        68.3        101.4                                      216.3      66.1        67.5        101.0                                      288.3      65.0        69.2        101.7                                      312.3      65.3        69.1        101.6                                      ______________________________________                                    

                  TABLE 15                                                        ______________________________________                                        CATALYST G -- 0.31% Pt; 0.15% Ir; 0.025% Ni; 0.73% Cl                         Run Conditions:                                                                           Aramco Naphtha at 1.0 ppm S                                                   1.0 W/Hr./W Space Velocity                                                   C.sub.5.sup.+ Product                                                                     Aromatics in                                           Hours on Feed                                                                            Yield       C.sub.5.sup.+ Product                                                                     Calculated                                 (End of Balance)                                                                         (Volume %)  (Volume %)  RON                                        ______________________________________                                        23.8       62.7        74.3        103.8                                      47.8       64.9        68.6        101.5                                      119.9      63.3        68.4        101.4                                      143.8      63.1        68.4        101.4                                      167.8      60.4        67.9        101.2                                      191.8      62.0        68.7        101.5                                      215.7      62.4        68.7        101.5                                      287.7      60.6        69.0        101.6                                      359.7      61.2        68.5        101.4                                      ______________________________________                                    

The more important aspects of these data are graphically illustrated,for convenience, by reference to the attached FIGS. 1 and 2. In each ofthe figures, the data obtained for the series of runs employingCatalysts A, B, C and D are plotted in terms of C₅ ⁺ Product Yield(volume %), which is a measure of the selectivity of the catalysts, andthe Aromatics Concentration (volume %) of the C₅ ⁺ Product, which is ameasure of the activity of the catalysts. The C₅ ⁺ Product Yield (volume%) is plotted on the vertical axis and the Aromatics Concentration(volume %) is plotted on the horizontal axis of each of the graphs.Additionally, the approximate Research Octane Number (RON), calculatedon the basis of aromatics concentration, is plotted on the horizontalaxes of each of the graphs.

For purposes of comparison, FIG. 1 depicts, graphically, data relatingto a large number of runs made with Catalysts A, B and C of which thedata given in Tables 2 through 6 are typical, and FIG. 2 depictsgraphical data relating to the same large number of runs made withCatalysts A and C, the same data being presented in both of the figuresfor comparison with runs made with Catalyst D. The activity-selectivitycurve for Catalyst A, presented graphically in FIGS. 1 and 2, is thusinclusive of the two runs for which data are listed in Tables 2 and 3,these data being typical of a larger group of runs from which the entireactivity-selectivity curve for Catalyst A is taken and employed as astandard for the 1.0 ppm sulfur Aramco feed runs. The solid unbrokenlines in the figures thus illustrate a standard to which other data maybe compared in a manner which is more easily understood than tabulardata. Likewise, the dashed line in these figures was drawn from a largerset of data of which the data in Table 4 are typical, again for CatalystA, but in this case for Baytown virgin naphtha utilizing 1.0 ppm sulfur.The ellipses depicted in the figures represent areas in which acollection of data points occur. The solid ellipse for Aramco feed andthe dashed ellipse for the Baytown feed represent, respectively, theareas in which the lined-out activity of Catalyst A occurs asillustrated in the data presented by Tables 2 and 4, respectively.Lined-out activity means a relatively constant or stable activity andselectivity which occurs after an early operating period of a run duringwhich the activity and/or selectivity usually significantly decreasesfrom an initially high level and/or increases after reaching a minimum.The dashed-dot ellipse of FIG. 1 represents an area in which the datafor the lined-out activity of Catalyst B occurs, the data tabulated inTable 5 being illustrative. The dotted lines depicted in the figuresrepresent a collection of data of which the run on Catalyst C astabulated in Table 6 is illustrative. In the case of this type ofcatalyst, there is typically no lined-out activity. The catalystdeactivates and data on any single run moves from right to left alongthe dotted line (within the range of experimental error).

In FIG. 1, there is thus presented a summary of data, the lines andellipses made with each of Catalysts A and B for both the Aramco andBaytown virgin naphtha feeds, each containing sulfur at the 1.0 ppmlevel. Runs conducted with Catalyst C, also depicted on the graph, wereconducted only with the Aramco feed which contained no sulfur. The runsconducted by reforming the Aramco feed are presented in the figure bythe graphical data presented at the lower portion of the sheet, andthose conducted by reforming the Baytown virgin naphtha feed at theupper portion of the sheet. Runs conducted with Catalyst A on theBaytown virgin naphtha feed are depicted (at the upper portion of thesheet) in the figure by a broken or dashed black line, and the lined-outactivity of the catalyst is depicted by the dashed line elipse withinwhich would lie a collection of points representative of the lined-outactivity of the catalyst. The same lines and areas of lined-out activityfor Catalyst A at the same sulfur concentration (1.0 ppm) for bothfeeds, and Catalyst C, on Aramco feed only, are also presented in FIG.2.

Runs made with Catalyst D on both the Aramco feed and the Baytown virginnaphtha feeds at sulfur levels of 1.0 ppm are plotted as clusters ofpoints on FIG. 1, and runs with Catalyst D made on both the Aramco andBaytown virgin naphtha feeds at sulfur levels of 0.4 ppm are plotted asclusters of points on FIG. 2. In contrasting these data with the datapresented for Catalysts A, B and C (FIG. 1) and Catalyst A and C (FIG.2), a number of observations are apparent concerning the effectivenessof platinum-iridium-nickel catalysts, as represented by Catalyst Dvis-a-vis platinum and platinum-iridium catalysts generally.

Referring to FIG. 1, it will be observed that in treating the Aramcofeed at the 1 ppm sulfur level, the platinum-iridium-nickel catalyst(Catalyst D) is only slightly lower in activity than theplatinum-iridium catalyst (Catalyst A), albeit the former contains onlyabout one-half as much iridium. On the other hand, Catalyst D hassuperior selectivity, providing 1-2% better C₅ ⁺ Product Yield atconstant octane. Thus, with only the catalyst changed, for a decrease ofabout 1 RON, a selectivity advantage of 1-2% is gained, and only aboutone-half as much iridium is used in preparation of the catalyst.

A catalyst similar in composition to Catalyst D, except that it containsno nickel, but only platinum and iridium in equal concentration, i.e.,Catalyst B, is a poorer catalyst. The lined-out activity of Catalyst Bthus produces a C₅ ⁺ product about 4 RON below that of Catalyst D at thesame conditions of operation. The selectivity of Catalyst D at loweroctane number levels also is generally better than that of Catalysts Aand B at the same octane levels.

When Catalyst D is compared with Catalyst A, again as shown in FIG. 1wherein data regarding the performance of these catalysts is depicted asin processing Baytown naphtha feed at the 1.0 ppm sulfur level, it isseen that Catalyst D provides a 1 to 11/2 percent yield advantage, atgiven RON level, over Catalyst A. Catalyst D, on the other hand,possesses about the same activity as a catalyst which contains abouttwice as much iridium, but no nickel. Thus, even though the advantagesof the platinum-iridium-nickel catalysts are not as sharplydistinguished as with the more difficult paraffinic feeds, theadvantages are nonetheless present.

Referring to FIG. 2, it will be observed that in treating the Aramcofeed at the 0.4 ppm sulfur level, that Catalyst D has about the sameactivity as Catalyst A (at its optimum sulfur level of 1.0 ppm), but theformer shows a selectivity advantage ranging from 1-3 percent greaterthan Catalyst A. Moreover, even at lower octane numbers, Catalyst Dmaintains this relative advantage over Catalyst A.

In the runs conducted with Catalysts A and D which utilized Baytownvirgin naphtha feed containing 0.4 ppm sulfur, it is apparent thatCatalyst D possesses both an activity and selectivity advantage overCatalyst A. Thus, at a given octane level, Catalyst D, at optimumconditions, provides from 2-3 percent C₅ ⁺ Product Yield advantage.Likewise, Catalyst D is more active than Catalyst A, at similaroperating conditions, each with its optimum feed sulfur level, CatalystD providing about a 11/2 RON advantage.

From these series of data, it is apparent that the incorporation ofnickel with platinum-iridium catalysts makes these catalysts moresulfur-tolerant. The substitution of nickel for iridium actuallyproduces a superior catalyst. In other words, platinum-iridium-nickelcatalysts are superior to platinum-iridium catalysts when thesedifferent catalysts are each operated at their optimum conditions. Infact, as illustrated by the data, even though Catalyst D operatedeffectively at the 1 ppm sulfur level, and provided advantages over itsbimetallic counterpart, its performance is even better at the 0.4 ppmsulfur level where Catalyst A cannot operate effectively. Anotheradvantage is that the use of large amounts of nickel in these catalystsis unnecessary, the smaller amounts of nickel being more effective thanthe larger concentrations. For example, Catalyst D, which containsone-half as much nickel as Catalyst E, shows superior activity andselectivity as contrasted with the latter. This is shown by comparisonof Tables 7 and 13. Likewise, Catalyst F and G show poorer activity andselectivity than Catalyst D, as shown by comparisons between Table 7 andTables 14 and 15. Comparing Catalysts E, F and G (Tables 13, 14 and 15)with Catalyst B (Table 5 ), similar to the former catalysts butcontaining no nickel, it becomes apparent that all threenickel-containing catalysts exhibit no significant activity advantagebut definitely show a selectivity advantage amounting to about 1% yieldat any give octane. All nickel levels appear to provide selectivityadvantages over the same catalyst, without the nickel. The low level ofnickel, however, provides both activity and selectivity as contrastedwith high nickel or with similar catalysts containing no nickel.

It is essential that the catalyst composition of this invention containthe triumvirate of metals--viz., platinum, iridium and nickel, depositedor otherwise incorporated, preferably impregnated, upon a porousinorganic oxide base in catalytically active concentrations. Thecatalytically active metals can be present, e.g., as metallic metal, oras oxides, chlorides, oxychlorides, aluminates, carbides, hydrides, orsulfides of the metal, or as mixtures thereof with these and other lesseasily describable structures. Under the varying conditions of formingand using the catalysts, it is likely that the metals will vary in theiractual distribution as oxides, chlorides, oxychlorides, aluminates,carbides, hydrides, sulfides, or reduced forms of the metals, ormixtures thereof with these and other less easily describablestructures. The metals, however, are calculated on the basis of metallicmetal. The catalytically active metals ar composited with the porousinorganic oxide bases by methods known to the art. Preferably, themetals are simultaneously impregnated on the support and, afterimpregnation of the support by contact with an acid solution, orsolutions, of salts of the metals, the so-formed composite is dried atconditions ranging from about 200 to about 400°F., often at reducedpressure or in a stream of flowing gas, then further dried and calcinedat temperatures ranging up to about 1200°F. in an atmosphere which doesnot agglomerate the iridium or other metals. The catalyst then may becontacted in situ or ex situ with halogen, halogen precursor, halide orhalide precursor. Halogen, preferably chlorine, and next in preferencefluorine, is generally added at the time of catalyst preparation as thehalide acid in the metals impregnation solution. Additional halogen canbe added during reforming operations to maintain desired operatinglevels. The catalyst is then sulfided, generally by contact with H₂ S indilute gaseous mixture to convert at least some of the metals to thecorresponding sulfides. As with the halides, the feeds can be spikedwith sulfur compound, or other higher sulfur feed, to add sulfide to thecatalyst during operation. H₂ S, HCl, or other gases containing sulfuror halogen can also be added to the recycle gas streams to changecatalyst sulfur halide levels during operation.

It is apparent that various modifications and changes can be madewithout departing the spirit and scope of the present invention, anoutstanding feature of which is that the octane quality of varioushydrocarbon feedstocks, inclusive particularly of paraffinic feedstocks,can be upgraded and improved.

Having described the invention, what is claimed is:
 1. A catalystsuitable for conversion of hydrocarbons comprising a composite of anacidic porous inorganic oxide support, platinum in concentration rangingfrom about 0.1 to about 1.0 percent, iridium in concentration rangingfrom about 0.1 to about 1.0 percent, and nickel in concentration rangingfrom about 0.0010 to about 0.0050 percent, based on the total weight ofthe catalyst, the atom ratio of the platinum:iridium ranging from about0.25:1 to about 5:1.
 2. The catalyst of claim 1 wherein the compositecomprises from about 0.1 to about 2.5 percent halogen.
 3. The catalystof claim 2 wherein the halogen is chlorine.
 4. The catalyst of claim 1wherein the composite contains from about 0.5 to about 1.5 percenthalogen.
 5. The catalyst of claim 1 wherein the porous inorganic oxidesupport is alumina.
 6. The catalyst of claim 1 wherein the compositecontains from about 0.001 to about 2 percent sulfur.
 7. The catalyst ofclaim 1 wherein the composite contains from about 0.01 to about 0.1percent sulfur.
 8. A reforming catalyst comprising a composite ofalumina, platinum in concentration ranging from about 0.1 to about 1percent, iridium in concentration ranging from about 0.1 to about 1percent, nickel in concentration ranging from about 0.0010 to about0.0050 percent, chlorine in concentration ranging from about 0.5 toabout 1.5 percent, and sulfur in concentration ranging from about 0.001to about 2 percent, the atom ratio of the platinum:iridium ranging fromabout 0.25:1 to about 5:1.
 9. The catalyst of claim 8 wherein the sumtotal amount of platinum and iridium ranges from about 0.3 to about 1percent.
 10. The catalyst of claim 8 wherein the sum total amount ofplatinum and iridium ranges from about 0.45 to about 0.70 percent.
 11. Aprocess for improving the octane quality of naphthas comprisingcontacting the said naphtha at reforming conditions with a compositecomprising a porous inorganic oxide support, platinum in concentrationranging from about 0.1 to about 1 percent, iridium in concentrationranging from about 0.1 to about 1 percent, and nickel in concentrationranging from about 0.0010 to about 0.0050 percent, based on the totalweight of the catalyst, the atom ratio of the platinum:iridium rangingfrom about 0.25:1 to about 5:1.
 12. The process of claim 11 wherein thesum total concentration of platinum and iridium ranges from about 0.3 toabout 1 percent.
 13. The process of claim 11 wherein the compositecomprises from about 0.1 to about 2.5 percent halogen.
 14. The processof claim 11 wherein the composite comprises from about 0.5 to about 1.5percent halogen.
 15. The process of claim 14 wherein the halogen ischlorine.
 16. The process of claim 11 wherein the porous inorganic oxidesupport is alumina.
 17. The process of claim 11 wherein the catalystcontains from about 0.001 to about 2 percent sulfur.
 18. The process ofclaim 17 wherein the catalyst contains from about 0.01 to about 0.1percent sulfur.
 19. The process of claim 11 wherein reforming isconducted at temperatures ranging from about 600°F. to about 1050°F., atpressures ranging from about 50 psig to about 750 psig, at spacevelocities ranging from about 0.1 to about 25 W/Hr./W, and at hydrogenrates ranging from about 1000 to about 10,000 SCF/Bbl.
 20. The processof claim 19 wherein temperatures range from about 850°F. to about1000°F., pressures range from about 100 psig to about 250 psig, spacevelocities range from about 1.0 to about 5.0 W/W/Hr., and the hydrogenrate ranges from about 2000 to about 5000 SCF/Bbl.